In the operation of the heart, returning blood enters the right atrium and passes through the tricuspid valve into the right ventricle. From there, blood is pumped through the pulmonary valve and the pulmonary artery to the lungs. Oxygenated blood enters the left atrium and passes into the left ventricle through the mitral valve. Healthy mitral valve leaflets “coapt” or meet near the middle of the blood flow path and are attached to papillary muscles within the interior of the left ventricle by a number of stringy chordae tendinae. During systole, the mitral valve closes and the aortic valve opens, thus preventing blood from regurgitating into the left atrium and forcing blood into the aorta, and from there throughout the body. Because of the high pressures associated with the left ventricle during systole, proper mitral valve function to prevent back flow through the system is extremely important.
Mitral regurgitation is one of the most common valvular malfunctions in the adult population. Mitral valve prolapse is the most common cause of mitral regurgitation in North America and is believed to affect at least 5 to 10 percent of the population in the U.S. Women are affected about twice as often as men. Mitral valve prolapse has been diagnosed as Barlow's syndrome, billowing or balloon mitral valve, floppy mitral valve, floppy-valve syndrome, myxomatous mitral valve, prolapsing mitral leaflet syndrome, or systolic click-murmur syndrome. Some forms of mitral valve prolapse seem to be hereditary, though the condition has been associated with Marfan's syndrome, Grave's disease, and other disorders.
Barlow's disease is characterized by myxoid degeneration and appears early in life, often before the age of fifty. Patients typically present with a long history of systolic murmur and may experience valve infection, arrhythmias and atypical chest pain. Some cases are asymptomatic, but a pronounced midsystolic click with or without late systolic murmur, usually indicates the presence of this disorder. South African cardiologist John B. Barlow was the first to interpret this auscultation syndrome, known for decades as an expression of a mitral valve prolapse. In Barlow's disease, one or both leaflets of the mitral valve protrude into the left atrium during the systolic phase of ventricular contraction. The valve leaflets are thick with considerable excess tissue, producing an undulating pattern at the free edges of the leaflets. The chordae are thickened, elongated and may be ruptured. Papillary muscles are also occasionally elongated. The annulus is dilated and sometimes calcified. Of course, some of these symptoms present in other pathologies, and therefore the present application will refer to mitral valve prolapse as a catch-all for the various diagnoses, including Barlow's syndrome.
FIG. 1 is an enlarged view of the left ventricle LV illustrating mitral valve prolapse, such as seen with Barlow's syndrome. One of the leaflets 20 of the mitral valve MV is shown thickened and lengthened from its normal configuration. As a result, the leaflet 20 is shown flopping upward into the left atrium LA. This excess tissue, or redundancy, often prevents the anterior and posterior leaflets from properly coapting, resulting in mitral regurgitation.
In patients with degenerative mitral valve disease, valve repairs using mitral valvuloplasty valve reconstruction, or annuloplasty have been the standards for surgical correction of mitral regurgitation and have provided excellent long-term results. A rigid support ring (e.g., Carpentier-Edwards Classic®), a semi-flexible ring (e.g., Carpentier-Edwards Physio®), or a flexible ring (e.g., Cosgrove-Edwards®) may be used. Other repair techniques include: quadrangular resection of the prolapsing portion of the posterior leaflet; transposition of the posterior leaflet to the anterior leaflet to correct anterior-leaflet prolapse; commissurotomy combined with ring annuloplasty; replacement of a chordae tendinae with sutures; and plication (or resection) of the anterior leaflet. A commonly used repair is the so-called “sliding technique” introduced by Dr. Alain Carpentier, which involves quadrangular resection followed by cutting the posterior leaflet and reconstruction to shorten this leaflet.
The advantages of repair over replacement have been widely demonstrated; however, studies have shown that mitral valve repair is performed in less than half of surgical procedures involving the mitral valve, and even fewer repairs are performed in patients with complex mitral regurgitation (e.g., Barlow's disease, bileaflet prolapse and annular calcification). Despite adequate tissue resection and placement of an annuloplasty ring or band, patients may have residual mitral regurgitation associated with systolic anterior motion (SAM) of the anterior leaflet. SAM occurs when the elongated leaflet is pulled into the left ventricular outflow tract (LVOT). This leads to partial LVOT obstruction and hemodynamic instability. This scenario is not an uncommon incident following an otherwise successful mitral valve repair and can be very difficult to treat with existing repair techniques and devices, and may require mitral valve replacement rather than the preferred of valve repair.
One example of a prior art surgical resection technique for correcting mitral valve prolapse is seen in the sequence of FIGS. 2A-2F. FIG. 2A is a plan view of the mitral valve annulus in which the anterior leaflet 22 and posterior leaflet 24 do not properly coapt in the middle of the annulus. A somewhat smile-shaped gap is seen between the two leaflets. As mentioned above, this condition can result from a number of pathologies, though the particular pathology illustrated is that which often results from Barlow's syndrome. The surgical technique involves resecting a portion of the posterior leaflet 24 by first cutting along the dashed lines 26. FIG. 2B shows the posterior leaflet 24 after the portion indicated in FIG. 2A has been resected and an incision for sliding annuloplasty has been performed
FIGS. 2C-2E illustrate a progression of suturing operations in which first stabilizing sutures 28 are passed through the annulus 30 and then a plurality of fixation sutures 32 are used to reapproximate the posterior leaflet 24, thus shortening the posterior leaflet relative to the annulus 30. Finally, in FIG. 2F, an annuloplasty ring 34 has been implanted around the posterior aspect 36 of the annulus 30, generally corresponding to the perimeter of the posterior leaflet 24. A comparison of the size of the annulus 30 in FIGS. 2E and 2F illustrates the effect of the addition of the ring 34. That is, the annulus circumference has been reduced. More importantly though, the leaflets 22, 24 are shown properly coapting without the aforementioned gap.
In early 1990's, Dr. Ottavio Alfieri introduced the concept of edge-to-edge heart valve repair. This repair technique consists of suturing the edges of the leaflets at the site of regurgitation, either at the paracommissural area (eg: A1-P1 segments: para commissural repair) or at the middle of the valve (e.g.: A2-P2 segments: double orifice repair). Three patents disclosing various devices for performing such edge-to-edge procedures are U.S. Pat. No. 6,165,183 to Kuehn, et al., U.S. Pat. No. 6,269,819 to Oz, et al., and U.S. Pat. No. 6,626,930 to Allen, et al. Recently, the edge-to-edge technique has been used in conjunction with annuloplasty procedures for treating the pathology seen with mitral valve prolapse. The underlying bases for these techniques are to eliminate the primary regurgitant area by suturing the leaflet edge and decreasing leaflet mobility, and to correct leaflet redundancy, force coaptation, and restrict leaflet motion.
Despite accepted treatments for correcting mitral valve prolapse, for example Barlow's syndrome, there is a need for a simpler and more effective approach, preferably one that avoids the need for sliding annuloplasty. Sliding annuloplasty adds technical and skill intensive barriers that limit widespread adoption of mitral valve repair.